image: Refactor to use cas/ref engines instead of walkers

The validation/unpacking code doesn't really care what the reference
and CAS implemenations are.  And the new generic interfaces in
image/refs and image/cas will scale better as we add new backends than
the walker interface.

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

cmd/oci-image-tool/autodetect.go

@@ -27,7 +27,6 @@ import (
 
 // supported autodetection types
 const (
-	typeImageLayout  = "imageLayout"
 	typeImage        = "image"
 	typeManifest     = "manifest"
 	typeManifestList = "manifestList"
@@ -43,7 +42,7 @@ func autodetect(path string) (string, error) {
 	}
 
 	if fi.IsDir() {
-		return typeImageLayout, nil
+		return typeImage, nil
 	}
 
 	f, err := os.Open(path)

cmd/oci-image-tool/create_runtime_bundle.go

@@ -26,7 +26,6 @@ import (
 
 // supported bundle types
 var bundleTypes = []string{
-	typeImageLayout,
 	typeImage,
 }
 
@@ -93,9 +92,6 @@ func (v *bundleCmd) Run(cmd *cobra.Command, args []string) {
 
 	var err error
 	switch v.typ {
-	case typeImageLayout:
-		err = image.CreateRuntimeBundleLayout(args[0], args[1], v.ref, v.root)
-
 	case typeImage:
 		err = image.CreateRuntimeBundle(args[0], args[1], v.ref, v.root)
 	}

cmd/oci-image-tool/unpack.go

@@ -26,7 +26,6 @@ import (
 
 // supported unpack types
 var unpackTypes = []string{
-	typeImageLayout,
 	typeImage,
 }
 
@@ -45,8 +44,8 @@ func newUnpackCmd(stdout, stderr *log.Logger) *cobra.Command {
 
 	cmd := &cobra.Command{
 		Use:   "unpack [src] [dest]",
-		Short: "Unpack an image or image source layout",
-		Long:  `Unpack the OCI image .tar file or OCI image layout directory present at [src] to the destination directory [dest].`,
+		Short: "Unpack an image",
+		Long:  `Unpack the OCI image present at [src] to the destination directory [dest].`,
 		Run:   v.Run,
 	}
 
@@ -86,9 +85,6 @@ func (v *unpackCmd) Run(cmd *cobra.Command, args []string) {
 
 	var err error
 	switch v.typ {
-	case typeImageLayout:
-		err = image.UnpackLayout(args[0], args[1], v.ref)
-
 	case typeImage:
 		err = image.Unpack(args[0], args[1], v.ref)
 	}

cmd/oci-image-tool/validate.go

@@ -28,7 +28,6 @@ import (
 
 // supported validation types
 var validateTypes = []string{
-	typeImageLayout,
 	typeImage,
 	typeManifest,
 	typeManifestList,
@@ -64,7 +63,7 @@ func newValidateCmd(stdout, stderr *log.Logger) *cobra.Command {
 
 	cmd.Flags().StringVar(
 		&v.ref, "ref", "v1.0",
-		`The ref pointing to the manifest to be validated. This must be present in the "refs" subdirectory of the image. Only applicable if type is image or imageLayout.`,
+		`The ref pointing to the manifest to be validated. This must be present in the "refs" subdirectory of the image. Only applicable if type is image.`,
 	)
 
 	return cmd
@@ -122,8 +121,6 @@ func (v *validateCmd) validatePath(name string) error {
 	}
 
 	switch typ {
-	case typeImageLayout:
-		return image.ValidateLayout(name, v.ref)
 	case typeImage:
 		return image.Validate(name, v.ref)
 	}

image/config.go

@@ -18,13 +18,12 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"io"
 	"io/ioutil"
-	"os"
-	"path/filepath"
 	"strconv"
 	"strings"
 
+	"github.com/opencontainers/image-spec/image/cas"
+	"github.com/opencontainers/image-spec/image/structure"
 	"github.com/opencontainers/image-spec/schema"
 	"github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
@@ -49,41 +48,23 @@ type config struct {
 	Config       cfg    `json:"config"`
 }
 
-func findConfig(w walker, d *descriptor) (*config, error) {
-	var c config
-	cpath := filepath.Join("blobs", d.Digest)
-
-	f := func(path string, info os.FileInfo, r io.Reader) error {
-		if info.IsDir() {
-			return nil
-		}
-
-		if filepath.Clean(path) != cpath {
-			return nil
-		}
-
-		buf, err := ioutil.ReadAll(r)
-		if err != nil {
-			return errors.Wrapf(err, "%s: error reading config", path)
-		}
-
-		if err := schema.MediaTypeImageSerializationConfig.Validate(bytes.NewReader(buf)); err != nil {
-			return errors.Wrapf(err, "%s: config validation failed", path)
-		}
+func findConfig(engine cas.Engine, descriptor *structure.Descriptor) (*config, error) {
+	reader, err := engine.Get(descriptor.Digest)
+	if err != nil {
+		return nil, err
+	}
 
-		if err := json.Unmarshal(buf, &c); err != nil {
-			return err
-		}
+	buf, err := ioutil.ReadAll(reader)
+	if err != nil {
+		return nil, errors.Wrapf(err, "%s: error reading manifest", descriptor.Digest)
+	}
 
-		return errEOW
+	if err := schema.MediaTypeImageSerializationConfig.Validate(bytes.NewReader(buf)); err != nil {
+		return nil, errors.Wrapf(err, "%s: config validation failed", descriptor.Digest)
 	}
 
-	switch err := w.walk(f); err {
-	case nil:
-		return nil, fmt.Errorf("%s: config not found", cpath)
-	case errEOW:
-		// found, continue below
-	default:
+	var c config
+	if err := json.Unmarshal(buf, &c); err != nil {
 		return nil, err
 	}
 

image/descriptor.go

@@ -17,81 +17,23 @@ package image
 import (
 	"crypto/sha256"
 	"encoding/hex"
-	"encoding/json"
-	"fmt"
 	"io"
-	"os"
-	"path/filepath"
 
+	"github.com/opencontainers/image-spec/image/cas"
 	"github.com/opencontainers/image-spec/image/structure"
 	"github.com/pkg/errors"
 )
 
-type descriptor structure.Descriptor
-
-func findDescriptor(w walker, name string) (*descriptor, error) {
-	var d descriptor
-	dpath := filepath.Join("refs", name)
-
-	f := func(path string, info os.FileInfo, r io.Reader) error {
-		if info.IsDir() {
-			return nil
-		}
-
-		if filepath.Clean(path) != dpath {
-			return nil
-		}
-
-		if err := json.NewDecoder(r).Decode(&d); err != nil {
-			return err
-		}
-
-		return errEOW
-	}
-
-	switch err := w.walk(f); err {
-	case nil:
-		return nil, fmt.Errorf("%s: descriptor not found", dpath)
-	case errEOW:
-		// found, continue below
-	default:
-		return nil, err
-	}
-
-	return &d, nil
-}
-
-func (d *descriptor) validate(w walker) error {
-	f := func(path string, info os.FileInfo, r io.Reader) error {
-		if info.IsDir() {
-			return nil
-		}
-
-		digest, err := filepath.Rel("blobs", filepath.Clean(path))
-		if err != nil || d.Digest != digest {
-			return nil // ignore
-		}
-
-		if err := d.validateContent(r); err != nil {
-			return err
-		}
-
-		return errEOW
-	}
-
-	switch err := w.walk(f); err {
-	case nil:
-		return fmt.Errorf("%s: not found", d.Digest)
-	case errEOW:
-		// found, continue below
-	default:
-		return errors.Wrapf(err, "%s: validation failed", d.Digest)
+func validateDescriptor(engine cas.Engine, descriptor *structure.Descriptor) error {
+	reader, err := engine.Get(descriptor.Digest)
+	if err != nil {
+		return err
 	}
 
-	return nil
+	return validateContent(descriptor, reader)
 }
 
-func (d *descriptor) validateContent(r io.Reader) error {
+func validateContent(descriptor *structure.Descriptor, r io.Reader) error {
 	h := sha256.New()
 	n, err := io.Copy(h, r)
 	if err != nil {
@@ -100,13 +42,15 @@ func (d *descriptor) validateContent(r io.Reader) error {
 
 	digest := "sha256:" + hex.EncodeToString(h.Sum(nil))
 
-	if digest != d.Digest {
+	if digest != descriptor.Digest {
 		return errors.New("digest mismatch")
 	}
 
-	if n != d.Size {
+	if n != descriptor.Size {
 		return errors.New("size mismatch")
 	}
 
+	// FIXME: check descriptor.MediaType, when possible
+
 	return nil
 }